Conventionally, data of each frame of digital terrestrial broadcasting is stored in a memory, and the data of each frame accumulated in the memory is transferred to a buffer circuit in a display control circuit by a DMA (Direct Memory Access) controller to be accumulated once. The display control circuit transmits a clock signal to a display device, and transmits the data for one pixel accumulated in the buffer circuit to the display device at an edge (such as a rising edge) of the clock signal. The display device loads the data inputted from the buffer circuit in the display control circuit at the edge of the clock signal to display the loaded data in a display.
The display device updates a display position of the display at the edge of the clock signal even if data to be transmitted to the display device is not stored in the buffer circuit in the display control circuit. Therefore, if no data to be transmitted to the display device is stored in the buffer circuit in the display control circuit while data is displayed, the data would be displayed in a display position which shifts from an original display position in which the data is to be displayed, for a clock number corresponding to a period for which no data to be transmitted to the display device is stored. The outline is shown in FIG. 10. Note that hereinafter, the state in which no data to be transmitted to the display device is stored in the buffer circuit is referred to as underflow.
FIG. 10A is a display image example when underflow does not occur, and FIG. 10B is a display image example when underflow occurs. As shown in FIG. 10B, when underflow occurs, a display position of a display image after an underflow occurrence position shifts from an original display position.
Therefore, a double buffer structure in which two memory areas for storing data for one frame in a memory is generally employed (refer to a patent document 1, for example). While data for one frame which is a display target for a display is displayed, data for next one frame is stored in a memory area which is different from a memory area in which the display target data is stored. This prevents a situation in which there is no data stored in a memory, which is to be transmitted to the buffer circuit in the display control circuit, and suppresses the occurrence of underflow.
Patent Document 1: Japanese Published Patent Application No. S58-35637